I remember the time when the news was out, can't remember the date but seems it took a while for them to implement on products. I think they also can't be changed like regular tubes (soldered on the board) but such a long lifespan might not make this a problem.

There are still too few products to say much but atleast they sound better than modern capasitors used on pedals/amps. The potential seems cool, hopefully we'll see more examples to have a better opinion in time.

.... I think they also can't be changed like regular tubes (soldered on the board) but such a long lifespan might not make this a problem. ...

With regular 12AX7s there are still more possibilities soundwise, because we can have different 12AX7s on slots V1, V2, V3, ... I mean: long plate, short plate, etc . As always, pros and cons! but nice to see that even tubes can have a facelift.

Side note I haven't heard of many class-d type poweramp, so as a concept we can say its very new tech. . I guess depending on the market new models can be introduced, they probably played safe maybe thinking of synth.s too.

And yeah as far as I know tube today are only used for musical equipment, glad although this limitation there is still enough interest for investment.